[ rickettsiosis: bacteriological aspects and diagnostic features]

ABSTRACT

Rickettsiae are gram-negative intracellular rods belonging to the family Rickettsiaceae, which currently includes only two genera Rickettsia and Orientia. The species within the genus Rickettsia are divided into two groups the spotted fever group [SFG] and typhus group [TG]. Rickettsiae are usually transmitted by ticks, mites, fleas and lice. After the arthropod bites or penetration through skin excoriations, the epithelial cell is the main target of the bacterium. At the site of inoculation, an eschar will appear, and then the bacteria can reach lymphatic and blood circulation leading to a rickettsemia. The bacteria will then reach several organs including skin rash, lung, brain, heart.. Since Rickettsiae are strict intracellular bacteria, the diagnosis of rickettsial diseases is often confirmed by serology which remains the most accessible tools to the routine laboratory. The microimmunofluorescence is the reference method. For detection and identification of rickettsia, various types of samples can be used such as skin biopsies at the eschar or rash, samples of whole blood or even ticks or fleas. The isolation of these bacteria is restricted to laboratories that can perform cell culture. PCR targeting different genes is sensitive and specific